One of related arts to the present invention is Patent Document 1, which proposes a method of enlarging a dynamic range of an output signal in response to the quantity of incident light in the array of pixels each including high-sensitive and low-sensitive photoelectric conversion elements. In this method, these photoelectric conversion elements are exposed through a single microlens to light to read out signals from these elements and to combine them.
Nonpatent Document 1 also proposes a method of enlarging a dynamic range using a photodiode, which has a capacitor for storing charges overflowing therefrom, by combining signals from charges stored in the capacitor.
Furthermore, Patent Document 2 proposes a method of storing a part of electric charges overflowing over a potential barrier. Patent Document 3 also describes a solid-state image pick-up device. In the solid-state image pick-up device, a light signal from an image pick-up area is converted using first and second photosensitive pixels to signal charges. These signal charges are read out into a vertical CCD and is transferred thereby, and then the transferred charges are further transferred using a horizontal CCD. The sensitivity characteristics of the first and second photosensitive pixels are different from each other. The signal charges of the first and second photosensitive pixels are read out at the same time.
Furthermore, there are many other methods which enlarge the dynamic range of the output signal in response to the quantity of incident light. A representative method among them combines plural signals generated in different exposure times. Since generating these signals in the two exposure times needs different processing in different timing, thereby distorting a moving object in an image from the signals.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2004-335803
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 2005-86082
[Patent Document 3] Japanese Unexamined Patent Application Publication No. 3-117281
[Nonpatent Document 1] Shigetoshi Sugawa et al., “A 100 dB dynamic range CMOS image sensor using a lateral overflow integration capacitor”, Dig. Tech. Papers, ISSCC, 2005, p. 352-353